Control effect of Orius similis on Frankliniella occidentalis based on the two-sex life table and the age-stage-specific predation rate.
Objective: Frankliniella occidentalis is an important agricultural invasive pest, and Orius similis is the dominant predator species in China. The objective of this study is to systematically evaluate the control effect of O. similis on F. occidentalis and the biological differences between this two species in the same area. Method: O. similis and F. occidentalis were collected from open field Capsicum annuum, then reared by fresh shoots with flowers of C. annuum for 2-3 generations under indoor condition, and the 2nd instar nymphs of F. occidentalis were feed to O. similis in the experiment. Growth, reproductive rate, predation rate were tested in Yunnan populations of O. similis and F. occidentalis using the two-sex life table and the age-stage-specific predation rate methods. Result: The different insect periods of O. similis and F. occidentalis have different levels of overlap during their developmental stages, and the survival rate of female adults of both insect species was higher than that of male adults. O. similis nymph has 5 instars, while F. occidentalis has 4 instars. Compared with F. occidentalis, O. similis has a longer nymph duration and shorter adult lifespan, and the survival rate of each developmental period was lower than that ofF. occidentalis, especially the survival rate of female adults was obviously lower than that of F. occidentalis. The probability of O. similis successfully developing from egg to female adult and male adult was 32.67% and 20.67%, respectively, which was lower than that ofF. occidentalis's 46.67% and 16.67%.F. occidentalis has a higher proportion of females within its population. The reproductive parameters (fx) of O. similis and F. occidentalis peaked at 22 d and 16 d during the whole developmental stages, respectively. O. similis has an average egg production of 42.00 eggs per female, which was significantly lower than that of theF. occidentalis (59.86 eggs). The population net reproduction rate (R0), gross reproduction rate (GRR), intrinsic rate of increase (r) and finite rate of increase (λ) in O. similis were lower than those ofF. occidentalis, while the mean generation time (T) and population doubling time (DT) in O. similis were longer than those of F. occidentalis. The population prediction results showed that the individuals of F. occidentalis reached 9.66 times than that of O. similis after 90 days of population growth and development, and the number of female adults reached 17.15 times. The predation rate of O. similis on the 2nd instar nymphs of F. occidentalis gradually increases with age, and the population characteristic net predation rate (C0) of F. occidentalis was 140.81, and the transformation rate (Qp) was 9.05. The average predation of female and male adult O. similis to F. occidentalis 2nd instar nymphs was 159.67 and 86.00 individuals, respectively. Conclusion: O. similis population can finish its life history and has stable population growth when fed by F. occidentalis. F. occidentalis has a stronger population growth potential than that of O. similis under the same conditions. As an important natural enemy of F. occidentalis biological control, O. similisshould be released 10-20 d before F. occidentalis outbreak and continuous released during F. occidentalis outbreak, this can achieve better control effects to F. occidentalis.